Electron discharge device structure



Nov. 4, 1958' R. P. WATSON ET AL 2,359,371

ELECTRON DISCHARGE DEVICE STRUCTURE Filed April 9, 1954.

Inventor-s Robert P. Watson,

Newton D. Jones,'

bgWmmW Th ei1- tto e ilnited rates Patent O ELECTRON DISCHARGE DEVICE STRUCTURE Robert P. Watson, Schenectady, and Newton D. Jones, Scotia, N. Y., assignors to General Electric Company, a corporation of New York Application April 9, 1954, Serial No. 422,091

8 Claims. (Cl. 313-244) This invention relates to electron discharge devices and more particularly to improvements in the mounting of the electrodes employed therein.

The principal object of this invention is to provide an improved arrangement for mounting the active cathode surface in parallel plane vacuum tubes.

Another object is to provide an arrangement which accurately positions the active cathode surface in relation to other electrodes in an electron discharge device.

A still further object is to provide means for accurately mounting a cathode and another electrode in an electron discharge device.

In high frequency electron discharge devices it has been found expedient to support a circularly shaped active cathode area by a structure adapted to symmetrically conduct current to the cathode. This structure generally comprises a metal foil cylinder across one end of which the active cathode surface is provided. While such a construction has many advantages in addition to the symmetrical conduction of current, it also involves certain difficulties with reference to the accurate spacing of the active cathode surface in relation to the other electrodes in the device. In the past it has been the practice to support the active cathode surface from a location many times more distant from the active cathode surface than the distance from the cathode surface to the electrode to which cathode spacing is important. Accurate spacing and parallelism has thus been rendered exceedingly difficult.

In accordance with the teachings of this invention a single insulating member supports both the cathode and the electrode to which the cathode spacing is important. An accurately positioned reference surface is provided on this insulator, and the cathode and said electrode are accurately positioned With respect thereto. Furthermore, the cathode is permanently bonded to the insulator in close proximity to the active cathode surface to facilitate accurate spacing and parallelism between the cathode and the adjacent electrode.

For further objects and advantages and for a better understanding of this invention, attention is directed to the following description and to the accompanying drawings, and thosefeatures which constitute this invention and which are desired to be protected herein are pointed out with particularity in the appended claims. In the drawing:

Fig. 1 is a sectional view of an electron discharge device employing one embodiment of this invention; and

Fig. 2 is a sectional view of the device of Fig. 1.

Referring to the drawing, the electron discharge device there illustrated includes three circular metal members, 1, 2, and 3 which are arranged in spaced relationship and separated from one another by insulating cylinders 4 and 5 sealed between them. Both the metal members 1, 2, and 3 and the cylinders 4 and 5 are of progressively decreasing diameters from one end to the other so that the tube has a step-wise configuration. An anode 6 in the form of a cylinder extends through a central opening 7 in an annular disk 8 which spaces the anode from member 3. This anode is provided at its upper extremity with a cylindrical terminal 9 and at its lower extremity with a plane surface 10. A grid in the form of an annular metallic washer 11 with parallel wires 12 mounted across the aperture thereof is supported on an annular spacer 13 which rests upon an accurately ground, plane annular surface 14 provided on cylinder 5.

In the embodiment shown cylinder 5 is provided with a central opening 15 which, as can be seen by reference to Fig. 2, is triangular in cross-section. Below the grid and in cooperative relation with both the grid and anode there is provided a cathode having an active or electron emissive surface 16. The supporting structure for the active surface is of hollow cylindrical configuration and consists of a thin walled tubular member 17, preferably constructed of metal foil, a metallic sleeve or eyelet 18, and a metallic disk 19. Eyelet 18 is fastened, as for example by welding, to the under side of disk 19 and disk 19 is fastened about the periphery thereof to one end of tubular member 17.

Tubular member 17 which is of a diameter slightly less than the geometric height of the triangle defined by the periphery of central opening 15 in cylinder 5, is interposed within opening 15 and is brazed or soldered thereto at the points of abutment such as at 20, 21, and 22. These points of abutment are in close proximity to surface 16 such that the problem of parallelism is made less acute. To facilitate the brazing or soldering operation, the lower surface 23 of cylinder 5 is provided with a thin metal coating, indicated by stippling designated 23a in Figure 2 by any of several well-known methods. The brazing solder is preferably a metal or alloy which melts in the range of 1000 degrees centigrade so as to enable tube processing without a loss of rigidity of the cathode structure. The metal coating 23a and the brazing material or solder at the points of abutment 20, 21, and 22 provide a current conducting path between member 17 and metal member 2 which is the cathode terminal for the over-all electron discharge device.

Within the cathode structure and, more specifically, Within the depending sleeve or eyelet 18, there is provided a filamentary heater 24 which suitably consists of a double helix of tungsten or any other of the wellknown metals or alloys suitable for use as heating filaments in electron discharge devices. 0ne of the lower leads 25 is connected to eyelet 18 and the other lower lead 26 is connected to a solid, cylindrical electric terminal 27. Heating current may thus be supplied to heater 24 from a source of voltage, not shown for purposes of clarity, which is connected between member 2 and terminal 27.

Anode 6 is provided with a circular flange 28 near the lower extremity thereof which abuts against a surface on the under side of disk 8 and fixes the distance between disk 8 and anode surface 10. An annular insulating cylindrical spacer 29 is sealed between member 1 and terminal' 27, which has one end positioned within the aperture 30 of this spacer. Annular spacer 31 together with washer 11 and disk 8 fixes the interelectrode distance between the anode and the grid and also between the anode and the cathode.

In order to insure an accurate cathode to grid spacing in discharge devices of this type when manufactured on a quantity production basis, we have found this construction superior to any known in the prior art. In fabricating such a device, surface 14 is ground flat or planar to serve as a reference plane in the assembly of the device. The supporting structure for the cathode including eyelet 18, disk 19, foil 17, and heater 24 is assembled and positioned Within aperture 15 of cylinder 5, and the surface of disk 19 is positioned substantially parallel to the reference plane defined by surface 13. This may conveniently be accomplished with the help of a jig fixture. The cathode supporting structure is then bonded to cylinder 5 by brazing or by some other suitable process to provide a firm mechanical support for the cathode. The upper surface of disk 19 is then coated with a material having goodelectron emission characteristics to provide an active'cathode-surface; This coating is then machined or planed flat and parallel to the reference plane defined by surface 14. This same planing or machining operation is employed to accurately fix the distance between the plane of surface 14 and-the plane defined by the active cathode surface 16. Washer 11 provided therein with the centrally located foraminated aperture may be positioned directly on surface '14 or on a spacer such as spacer 13 and held tightly against surface 14 by spacer 31 during the sealing operation of the discharge device.

While this invention has been described by reference to a particular embodiment, thereof, it will be understood that-numerous modifications may be made by those skilled in the art without departing from the invention. We therefore, aim in the appended claims to cover all such equivalent variations as come within the true spirit and scope of the invention. 1

What we claim as new anddesire to secure by lietters Patent of the United States is: I

1. An electrode assembly comprising an insulating tubular member having a metallic layer. on the transverse surface at one end thereof, a cathode assembly extending into said tubular member from said one end and including a hollow metallic cathode support sleeve bonded directly to said metallic layer, and an electrode assembly mounted across the other end of said tubular member.

2. An electrode assembly for an electron discharge device comprising a tubular insulating member having an open end and a closed end with an aperture in said closed end, a metallic layer on the transverse outer surface of said closed end of said insulating member, a hollow metallic sleeve extending into said insulating member through said aperture and brazed to said insulating member adjacent the inner end of said sleeve, an electron emissive disk positioned across said inner end of said sleeve, and a foraminous member mounted directly across the open end of saidinsulatingmember.

3. An electrode assembly comprising an insulating tubular member having a closed end provided with an aperture therein and also having an open end, a metallic layer on the transverseouter surface of said closed end, a hollow metallic tube positioned within said aperture and brazed directly to said metallic layer at at least one point in close proximity to one end of said tube, and an electrode mounted on said one end of said tube, whereby said electrode is substantially free from vibration.

4. In an electron discharge device, a tubularinsulating member having an open end and a closed end with an aperture therein, a metallic layer on the transverse outer surface of said closed end of said insulating member and about the edge of said aperture, a hollow metallic tubular member having a closed end and positioned within said aperture, said metallic tubular member being brazed to said metallic layer at the edge of said aperture and adjacent the closed end of said metallic tubular member and a coating of electron emissive material in juxtaposition with the outer surface of the closed end of said metallic tubular member and which has the outer surface thereof positioned a set distance from the open end of said insu-- lating members.

5. In an electron discharge device, a hollow thin walled electron conducting tubular member, an electron emissive disk mounted at one end of said tubular member, a hollow insulating member of larger cross-section thanand concentrically located with and surrounding said conducting tubular member, an inwardly extending portion of said insulating member, a metal surface on said inwardly projecting portion, and said conducting tubular member extending on both sides of said inwardly projecting portion of said insulating member and being brazed to said metal surface on said inwardly extending portion of said insulating member.

6. An electrode assembly comprising an insulative tubular member having a metallic layer on the transverse surface at one end thereof, a cathode assembly in said tubular member including a hollow metal' sleeve extending into said tubular member and bonded intermediate the ends thereof to-said metallic layer, and a metal cylindrical contact bonded "to said one end of said insulative tubular member outwardly of said hollow metal sleeve, whereby said metallic layer on said transverse surface of said tubular member is efiective for making an electrical connection between said hollow metal sleeve and said cylindrical contact;

7. In an electric discharge device, an envelope, a tubular insulative member comprising a portion of the wall of said envelope said insulative member having a polygonal aperture including a plurality of straight sides in one end'thereof, a cathode assembly including a cylindrical support member disposed in said opening of said insulative member and making only circumferentially spaced line contacts therewith, said cathode support member being brazed to said insulative member 'at the points of said spaced contacts and thereby supported by said insulative member, and an electrode mounted across the opposite end of'sai'd insulative member in spaced relationship with said cathode assembly.

8. In an electric discharge device, an envelope, a tubular insulative member comprising a portion of the wall of said envelope, said insulative member having a reduced internal surface at one end, a metallic layer on the transverse surface of said one end, a metallic tube having one end extending into said insulative member through said one end'of said insulative member and brazed only at circumferentially spaced intervals to said metallic layer, an electrode mounted on said one end of saidmetallic tube in said insulating member, said envelope including an inwardly extending portion at the other end thereof, and another electrode mounted on said lastmentioned inwardly extending portion.

References Cited in the file of this patent UNITED STATES PATENTS 2,133,492 Vatter Oct. 18, 1938 2,402,119 Beggs June 18, 1946 2,411,184 Beggs Nov. 19, 1946 2,462,921 Taylor Mar. 1, 1949 2,495,259 Jackson Jan. 24, 1950 2,527,127 Gormley et al Oct. 24, 1950 2,609,518 Klopping Sept. 2, 1952 2,677,781 Drieschman May 4, 1954 2,699,517 Diener Ian. 11, 1955 2,719,185 Sorg et al Sept. 27, 1955 2,722,624 Doolittle Nov. 1, 1955 

